| Document and Entity Information | Sep. 30, 2022 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Sep. 30, 2022 |
| Entity Registrant Name | Legacy EJY, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-39800 |
| Entity Tax Identification Number | 98-1566891 |
| Entity Address, Address Line One | 3240 Hillview Ave |
| Entity Address, City or Town | Palo Alto |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94304 |
| City Area Code | 888 |
| Local Phone Number | 463-6569 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001830180 |
| Ordinary Shares [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common stock, $0.0001 par value per share |
| Security Exchange Name | NONE |
| Trading Symbol | ENJYQ |
| Warrant [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Warrants to purchase common stock |
| Security Exchange Name | NONE |
| Trading Symbol | ENJYWQ |
